Visit Metro Vancouver Levels site here and read the "River Flow m3/s"(CMS) (GREEN line) from the Capilano River gauge.
Use the chart below to roughly covert the CMS to the level indicated at the fish hatchery.
2; 20 cms
3; 30 cms
4; 50 cms
5; 70 cms
6; 90 cms
7; 115 cms
8; 140 cms
*9; 160 cms
*10; 200 cms
* these levels are over the weir and are approximations, be aware that a powerful and unavoidable recirculating hydraulic forms around these levels (video here https://vimeo.com/151471317)
Visit Metro Vancouver Levels site here and read the "River Level" (BLUE line) from the Seymour River gauge.
Use the graph below to roughly covert the gauge level to the level indicated on the rock.
You can view the rock on the river from the end of "Heritage Park Ln, North Vancouver"
This gauge is relevant for the Upper / "Middle" Mamquam, Mamquam Falls, and the Lower Mamquam (and kayak site) and may also be valuable for estimating flows in Skookum Creek. It's below all the power projects on the Mamquam, so it represents total flow in the river (the falls will have less flow than this gauge indicates and the correlation may change depending on generation rates).
Thanks to BC Whitewater and their ambassador Scott McBride for his work on this.